This examples shows how to get started with Adobe's Minion Pro fonts on Overleaf. The approach is simply to upload the Minion Pro OTF file(s) you need to Overleaf via the project menu, and then include them in your document using the fontspec package for XeLaTeX.

This example shows how to use the free Linux Libertine fonts on writeLaTeX. The Libertine font family provides serif fonts similar to Times New Roman.
The source code is based on The LaTeX Font Catalogue.

The XITS fonts provide a Times-like serif typeface for mathematical and scientific publishing. They provide a version of the STIX fonts enriched with the OpenType MATH extension, making them suitable for high quality mathematical typesetting with XeTeX and LuaTeX. XITS fonts are free and open source.

This example shows how to use Culmus fonts to write Hebrew in LaTeX. The Culmus Project provides a collection of Hebrew fonts for GNU/Linux and LaTeX communities.
Overleaf (formerly writeLaTeX) provides Culmus Fonts 0.7-r1 (as of 26 Jan 2014), in addition to the standard LaTeX fonts for Hebrew. (If you remove \usepackage{culmus}, you can see the standard fonts instead.) Also note that your Hebrew text must be UTF-8 encoded, and that Overleaf also supports entry of right-to-left (bidirectional) text in your LaTeX source.